显微超声法取根管内分离器械牙根应力三维有限元分析OA

Objective To analyze the effects of the microscopic ultrasonic method on root stress during the removal of instruments in the apical 1/3 separation of root canals with different curvature parameters using three-dimensional finite ele-ment analysis.Methods Six mandibular premolars extracted due to orthodontic treatment that met the inclusion criteria were divided into three groups according to the grade of root canal curvature,and then two isolated teeth with the same ben-ding radius in the same group were randomly divided into experimental group and control group.Both the control group and the experimental group samples were treated with K files to clear the root canal to size 20,and Sani S3 nickel titanium files were used for root canal preparation.The experimental group established a device separation model of 1/3 of the root apex to separate 4 mm K file(20#),and microsonic ultrasound was used to remove the separation device in the root canal for three-dimensional finite element analysis.Results(1)With the increase of the bending grade of the root canal,the peak value of the equivalent stress increased,and the stress concentration area transferred and mainly located on the inner side of the bending.(2)Within the same bending grade,the removal of the separating instrument changed the equivalent stress distri-bution of the tooth root;the tensile stress of the root increased and the flexural resistance reduced,which increased the risk of vertical root fracture,especially in the 45° direction of the tongue to the cheek under lateral loading.Conclusion(1)Equivalent stress distribution:the stress under vertical and lateral load concentrate in the upper 2/3 of the root,the maxi-mum value mainly locates in the root neck,and the apical 1/3 locates in the low stress area.(2)Maximum principal stress distribution:the maximum principal stress of the root under the two loads concentrate in the middle and upper 2/3 of the root,the maximum principal stress area locates on the lingual side under the vertical and tongue-to-cheek 45° load,and the maximum principal stress area locates on the buccal side under the buccal tongue.